HARRISBURG — For more than a century, governors and lawmakers have tried to change the state's uniform personal income tax, which makes most workers pay the same rate regardless of income.

All have failed.

The full Legislature has refused to vote on bills that would base income taxes on salary levels. Courts have struck down similar proposals. And voters have rejected the concept in referendums, which are required to alter Article 8, Section 1 of the state Constitution. It states: "All taxes shall be uniform, upon the same class of subjects … and shall be levied and collected under general laws."

But Tom Wolf, the Democratic candidate for governor, says he has a multi-pronged tax plan that will defy history by changing the personal income tax code — if he gets the chance to propose it by beating Republican Gov. Tom Corbett in November.

Others, however, question the legality and financial calculus of Wolf's plan.

The plan would drop the state's uniform personal income tax of 3.07 percent. In its place, Wolf would exempt a portion of wages, which would produce tax breaks for some workers and increase taxes for others.

Wolf says he would work with lawmakers to close corporate tax loopholes, which would drive up tax revenue. The state would take the revenue generated by the income and corporate tax changes and channel it to school districts and municipalities, allowing them to lower property taxes.

"One thing it does is to level the playing field," Wolf said in an interview Thursday. "That means making the tax system fairer across the board."

While stressing his plan is not final, Wolf offered an example of how it would work, using these hypothetical numbers: $40,000 salary, $30,000 exemption and a 5 percent tax rate.

The first $30,000 would be tax-exempt. So a worker would pay 5 percent on $10,000, resulting in an income tax bill of $500. That would represent a reduction of $421, or 46 percent, in what a worker would pay on his or her whole salary under the uniform tax.

A $250,000 wage earner would pay $12,500. That's $4,825, or 63 percent, higher than under the uniform tax.

But Wolf, a wealthy York County businessman and former state revenue secretary, could not say whether his tax shift would match or exceed the roughly $11.4 billion the state Revenue Department collected in income taxes in the fiscal year ending June 30, 2013. He also could not say how much corporate tax law changes would generate.

Citing the Revenue Department's year-old records, Wolf said he has not worked out the finer details of his plan to determine the exact portion of wages that would be exempt or how much savings could be generated for property tax relief.

"Who wins or loses? It's kind of hard to say because it's a broad group of people," Wolf said.

Claiming state records are too old is disingenuous, said Corbett campaign spokesman Chris Pack. The Revenue Department's publicly available records offer enough information for Wolf to give voters more details about how his plans would affect workers, Pack said.

"He's choosing not to because it's politically convenient for him not to," Pack said.

Based on Wolf's public statements, Pack said, a married couple who work as teachers would see a tax increase and they could not as easily afford it as Wolf, a millionaire.

Wolf said he cannot use old Revenue Department numbers, saying it would not generate an accurate picture of his plan. As proof, he cited the Corbett administration's 2013-14 revenue projections that came in about $700,000 below estimates.

To spend more money on public schools and other areas as he has proposed, Wolf must generate more revenue, said G. Terry Madonna, pollster and political science professor at Franklin & Marshall College in Lancaster. That means Wolf will have to offer more concrete information about his plan or face continued criticism, Madonna said.

"So Republicans are going to make the argument — tax hike, tax hike, tax hike," he said. "And it would be a tax hike for people over a certain amount of money, and we don't know where that threshold would be."

Between 1913 and 1937, the Legislature tried more than a dozen times to pass a bill that would set up a constitutional amendment question on enacting a graduated income tax, according to an article in the July 1960 edition of "Pennsylvania History: A Journal of Mid-Atlantic Studies." In 1913 and 1937, lawmakers watched voters reject graduated income tax amendments, the article says.

In 1971, Gov. Milton Shapp and lawmakers tried to enact a graduated income tax, similar to the Internal Revenue Service formula, without voter approval. The Supreme Court struck it down. Voters In 1989, by more than 2-to-1, crushed Gov. Robert P. Casey's referendum that would have allowed local governments to enact a personal income tax to reduce property taxes.

Similar proposals involving the income tax or sales tax have not made it out of the Legislature in recent years.

But Wolf said he does not think his idea would need a referendum. Rather, he said, his plan would be based on another part of the state Constitution. Article 8, Section 2, allows the Legislature to create a special tax provision for poverty, Wolf said. His plan would replace existing poverty provisions, which allow for deductions for dependent children and other measures, with a uniform exemption for all.

However, Wolf in September told Keystone Politics, a self-proclaimed "source for liberal political news and commentary," that he would support a constitutional amendment to create a graduated income tax.

By making wealthier workers pay more, Wolf's plan is a graduated tax in disguise and would need a referendum, said Nathan Benefield, vice president of Policy Analysis for the Commonwealth Foundation, a free-market think tank in Harrisburg. It's more equitable to tax everyone at the same rate, he said.

Voters dislike tax talk if they do not understand it, Madonna said.

"There is an inherent skepticism in voters once you talk about taxes when they are not sure what it means and how they would be affected," he said.